import java.util.Random;
import java.util.Scanner;

/**
 * Created by dllo on 18/3/31.
 */
public class Test07 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入任意数字");
        int b = scanner.nextInt();
        int sum = 0;
        for (int i = 1; i <= b; i++) {
            sum=sum+i;
        }
        System.out.println(sum);
    }
}
